M13 revisited


Mark Stronge
  Comber, County Down, Northern Ireland
Photo Title
M13 revisited
Time and Date taken
13:04hrs BST, 2nd August 2004
Equipment used
Orion ED80mm, Vixen GP mount, 2inch WO diagonal, Vibration isolation pads
Capturing device used
Canon Digital Rebel 300D 6.3 Megapixel
Technical details

ISO400, 30seconds. Hand picked 5 frames out of 10, then aligned and stacked in Registax with final processing in Paint Shop Pro 8

Wide field frameFull resolution cropped
The left image is the full frame image from the camera rotated and resized.
The right image is a centre crop at full resolution.

Not until you start to image deep sky objects with long exposures do you realise how bad light pollution can be. Admittedly, the transparency was poor and the streetlights were making things worse, but when a 30 second exposure of sky is a bright orange, you DO feel like giving up altogether. Longer exposures would have been better but the tracking on the Vixen GP didn't seem to be as good as on previous occasions. The polar alignment may have been off slightly. I did do a dark frame but it turned out I didn't need to as the dark image was completely black with no noise apparent at ISO400 30seconds! Any visible noise is due to me trying to filter out the orange skyglow. This Canon 300D has great potential... The final image was corrected with north up, no mirror image was necessary. Image from Registax was histogram stretched, manually colour corected and a light unsharp mask was applied. Central star cluster was selected individually and gamma adjusted to brighten colours. In the original image, stars down to Mag17 are visible though, due to filtering the light pollution, stars are visible to approximately Mag13 in above images. Original frame showed structure to nearby NGC6207, IC4617 was just a dot.

Here's one of the rejected frames that shows a satellite going through M13.


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